There have been numerous attempts to create stable shoes that increase energy return and reduce the impact and stress created on various parts of the human body during walking, running, jumping and other forms of motion that occur when a person uses his/her feet to travel across a surface hereinafter referred to as self-propelled locomotion.
U.S. Pat. No. 4,941,273 (Gross) uses an elastic band that stores and returns energy linearly which is not desirable for the heavier fast paced loads encountered during strenuous physical activity.
U.S. Pat. No. 6,029,374 (Herr, et al.) uses a two and three coupled spring system whereby energy is absorbed at heel and toe strike; however this invention lacks a powerful arch spring that can be used by the ball of the foot for increased performance.
U.S. Pat. No. 5,875,567 (Bayley) uses a heel spring; however this invention also lacks a powerful arch spring that can be uses by the ball of the foot for increased performance.
Other designs, which have reached the marketplace, include air bladders that are not stable, have been known to blow open and are incapable of storing relatively large amounts of energy; coil springs that are heavy and not stable which has led to injuries; and elastomers and elastomeric foams which are used as the primary shock absorbing and energy storage and return materials, but they fail to achieve the higher efficiency energy returns that are possible with spring boards.
The present invention overcomes many of the deficiencies of the previous designs by incorporating into the shoe a light weight stable design with a powerful primary spring-arch spring made from spring boards and used by the heel and ball of the foot areas to store and return energy efficiently and to help absorb shock. In addition, embodiments of the present invention allow the spring boards to extend into the toe area to be used as toe springs to enhance the energy storage and return capabilities of the shoe.
Also, it is known that while some devices are excellent for storing and returning energy, other devices are better at absorbing shock. Embodiments of the present invention utilize a primary spring system which is excellent for storing and returning energy and a shock absorbing material which can also function as a secondary spring in order to achieve high efficiency energy returns while maintaining comfort and stability with the shoe.